Optical plural channel signal data processor



Feb. 11. 1969 w. A. BLIKKEN ETAL OPTICAL PLURAL CHANNEL SIGNAL DATAPROCESSOR Filed m 4. 1960 Sheet I of 4 Fig-E3.

hVV'NIORS BY A 1969 w. A. BLIKKEN ETAL OPTICAL PLURAL CHANNEL SIGNALDATA PROCESSOR Sheet '3 or 4 Filed lay ,4. 1960 INVENTORS WENDELL A.BLIKKEN guls J. CUTRONA A HUR 1.. lNGALLS EMMETT N. LEITH LEONARD J.PORCELLO BY M1...

ATTORNEY Feb. 11, 1969 w, BLJKKEN E'Q 3,427,104

' OPTICAL PLURAL CHANNEL smmu. mm rnocnssoa Filed May 4. 1960 Sheet 3 of4 INVENTORS WENDELLA. BLIKKEN LOUIS J. CUTRONA ARTHUR L. INGALLS EMMETTN. LEITH LEONARD J. PORCELLO Feb. 11, 1969 w. A. BLIKKEN firm. 3,427,104

OPTICAL PLFJRAL CHANNEL SIGNAL DATA PROCESSOR Filed Bay 4. 1960 Sheet 4014 INVENTORS WENDELL A. BLIKKEN LOUIS J. CUTRONA ARTHUR L. INGALLSEMMETT N. LEITH LEONARD J. PORCELLO ATTOR EY Wyml AGENT United StatesPatent 3,427,104 OPTICAL PLURAL CHANNEL SIGNAL DATA llA.Blikk m fi is!Cuts-one d wcnde en, H e an Arthur L. ln'galls, Ann Arbor, Emmett N.Leith, Plymouth, and Leonard J. Porcello, Ann Arbor, Mich assignors tothe-United States of America as represented by the Secretary of the-AirForce vFiled May 4. 1960, Ser'. No. 26,916 U.S. Cl. 355-2 10 Claims Int.Cl. G03b 27/00, 27 /32, 27/68 This invention relates to a device forsimultaneously processing wave trains in a great number of channels;wherein the wave trains in the various channels need not all be thesame.

One object of the invention is to provide a device which processesDoppler frequency target information for all ranges simultaneously frominformation obtained from an airborne coherent side-looking radar.

Another object is to provide a device to produce desired compressedsignals simultaneously in a great many channels from signals greatlydispersed in time or space by the use of optical techniques with noiseand undesired signals greatly reduced.

These and other objects will be more fully understood from the followingdetailed description taken with the drawing, wherein:

FIG. 1 is a diagrammatic illustration of radar target information withtargets separated in azimuth such as would appear on a film obtainedfrom the recording unit of an air-home coherent'side-looking radar;

FIG. 2 is another diagrammatic illustration of radar target informationwith targets separated both in azimuth and range;

FIG. 3 shows the target information of FIG. 1 as it will appear on afilm strip after processing in the devic of the invention;

FIG. 4 shows a three-dimensional view for a basic optical processoraccording to the invention;

FIG. 5 shows the optical system for the device of FIG. 4 for resolvingtarget information in the azimuth direction;

FIG. 6 shows the optical system for the device of FIG. 4 for resolvinginformation in the range direction;

FIG. 7 shows a modification of the device of FIG. 4 for providingcompensation for changes of focus with range;

FIG. 8 is a schematic showing of the reference mask used in the deviceof FIG. 7;

FIG. 9 shows the relative motion of the first order images as the filmis moved;

FIG. 10 shows a modification of the device of FIG. 7 which providesanother method for providing range compensation:

FIG. 11 shows another modification for providing range compensation. I

The radar used to obtain the information as represented in FIGS-land 2is a coherent radar, that is, it provides phase as well as amplitudeinformation on all received radar signals by comparison with a stablereference oscillater. As the radar is carried along by the aircraft, aradar pulse is transmitted and the amplitude and phase of the returningsignals from all targets are stored by recording on film. A shortdistance later another'pulse is transmitted and the return signals areagainreoorded on the film. Continuing in this fashion the radar phaseand amplitude history for each radar illuminated target is obtained overan extended distance of travel of the aircraft. All

of the phase information for each target adds-up to produce the'Dopplerhistory for each target from. the time it enters the radar beam until"it leaves the radar beam.

This information can be used to give an improved resolution in azimuth.

The processing program in azimuth, however, is a function of range sothat one needs a large number of computiug channels,each having therequired computer program for each particular range. The various rangeincrements may then be assigned to the appropriate computer channels. Toavoid the construction of many channels, a single channel may beprovided to scan all of the required programs sequentially insynchronism with the corresponding data for the different ranges. Thissystem requires a large bandwidth, a scanning system and a data storagesystem. Either of these systems constructed on an electronic basis willinvolve a great amount of equipment and therefore a great cost.According to this invention, an optical data processing system is usedwhich processes the Doppler frequency target information for all rangessimultaneously.

The operation of the system (for a given range) can be described as across-correlation of the signal with reference function which is areplica of the expected return from that range, the expected returnhaving a form determined by the geometry of the radar antenna-targetrelation. Alternatively, the operation of the system can be described interms of optical properties of the recorded signals. A recorded signalfrom a radar target is a substantially linearly frequency modulatedrecord, which resembles a diffraction grating with grating spacingvarying substantially linearly along its length, of a slice takenthrough a zone plate. Such structures have focal properties similar tothose of a lens, as likewise does the recorded signal. When the signalhistory brings the impingent light to focus, the resulting image is thehigh resolution image which is sought. The signals have focal lengthwhich is a function of range to the target. The reference functiondescribed above is, from this viewpoint, a variable focal length lenswhich has a different focal length for each channel and compensates forthe range variation of the signal focal length.

These two viewpoints are equivalent. However, some configurations arebest described from one viewpoint, some from the other.

The simplest form of the invention consists essentially of a lightsource, a slit for providingcoherent illumination, a collimator, asignal film, a cylindrical lens, a photographic lens, an analyzer slitand a recording film. This simple form of the invention can be used onlyfor a very limited range interval due to the change in focus with range.For a more extended range interval, means must be provided to correctfor the change in focus.

Referring more particularly to FIGS. 1 and 2 of the drawing, which showa graphical representation of the Doppler histories of targets as theywould appear on a strip of film from the recording unit of an air-bornecoherent side-looking radar. Reference numbers 21 and 22 in FIG. 1 showa graphical representation of the Doppler histories of two targetsseparated is azimuth. Reference direction. Thislight is passed throughthe optical systems 33 and 34 through the final slit 35 in mask 36 andonto the recording film 37. The signal function appears on the film 38,which passes between optical systems 33 and 34. Since the opticalsystems are different for range and azimuth: these systems will bedescribed separately, with reference to FIGS. 5 and 6.

In the azimuth direction, shown in FIG. 5, the light from the narrowslit 30 is made parallel by collimator lens 33. This light is thenbrought toa distant focus by a signal on film 38. The distant image isthen brought to focus on the final slit 35 bya camera lens 40. Therecording film 37 may be placed very near the final slit 35 to receivethe image. It is preferable, however, to provide a relay lens 41 toimage the slit 35 on the film, as shown in FIG. 7.

In the range direction, the light from the line sourcev proceeds throughlens 33 in the manner shown in FIG. 6 to illuminate the-signal film. Theillustration of the light path in FIG. 6 is for only one range. Acylindrical lens 42 works together with the camera lens 40 to image therange elements from the signal film onto the final slit. In the rangedirection, the light source and first slit simply determine the amountof light allowed through the system and thereby determine the brightnessof the image on the recording film. The astigmatie lens system 34 thusacts to integrate the signal in the azimuth direction while preservingthe range information in-the range direction.

The speed of recording film with respect to the speed of the signal filmis determined by the ratio of range reduction to azimuth reductionexisting on the signal film. If 10.000 yards is shown as 35 mm..in therange direction, this same ratio should exist in the azimuth dimensionso that the resulting image will be in proper proportion. However, thetwo ratios are not necessarily equal on the signal film, where, forexample, 10,000 feet in azimuth might be represented as 700 mm., while10,000 ft. in range might be represented as 35 mm. The equalization ofthe ratios is made by adjusting the speed ratio between signal film andrecording film. For the example stated, the recording film should move,4 the speed of the signal film in order to bring the image to properportions.

The system thus far described can be used over a limited range intervalonly as the image goes out of focusdue to a change in focus with achange in range.

FIG. 7 shows one system, which may be used to com pensatc for changes offocus with range which is inherent in the signal recording. v

In the system of FIG. 7 reference numeral 50 refers to a light sourcewhich may be any type of light source, for example; a mercury vaporlamp. The light from light source 50 is imaged upon a slit 51 in mask 52by means of a pair of lenses 53 and 54. The width of slit 51 isdetermined by a compromise between image sharpness and total lightintensity and, for the devices used, it has been between 20 microns and250 microns. The length of the slit is not critical.

Between the lenses 53 and 54 are provided a heat refleeting filter 55,to prevent heat from passing to the signal film and thereby damaging it,and an optical filter 56 to provide a monochromatic light for the dataprocessor which, for the system built, was an optical green filter.

A lens 57. is provided to cause parallel light in the azimuth directionto impinge on thereference function mask 58, which will be explained ingreater detail in connection with FIG. 8. Due to the difiractionetfectof the reference function, the distribution of light in the focalplane of lens 59 is a spectrum analysis of the spatial frequencies ofthe reference function. A slit 60 in. mask 61 is placed in theappropriate position in the focal plane of the lens'so that only thedesired signals can proceed further along the system, as will beexplained later. A lens 62 acts together with lens 59 to image-thereference function uponthe signal film 38. A weighting function filter63, which consists of a variable. density filter which graduallydecreases light transmission toward the edges of the reference mask, isprovided for the same reason that antennas are tapered toward their endswhich is to reduce side lobe efi'ects, as described at the bottom ofpage 452 and the top of page 453 of vol. 12 of the MIT RadiationLaboratory eries. The remainder of the system is the same as'FIG. 4.

vThe reference function on mask 58 the general configuration of which isshown in FIG. 8 consists-essentially of the ideal Doppler signalhistories for tangets at all ranges of the radar and thus can beconsidered to have alike number of functions thereon corresponding tothe functions on the signal film for all ranges of the radar. Thespacings between the lines in the actual mask used are much less than asshown in FIG. 8. Since the time that a target appears in the radar beamwill increase with range, thereference mask is wedge shaped.

The referencemask can be made in various ways. Two methods" have beenused. First, the mask is drawn by hand and then reduced to sizeandplaced on a transparency by photographic means. Alternatively, adevice used for ruling diffraction gratings has been used for producingthe mask. In either case, the mask is only an approximation to therequired'function, since the former is a two-valued function, beingeither transparent or opaque, while the latter is a continuous tone orshaded transparency. Specifically, the required referencefunction is ofthe form (+cos (x, y)), and the actual mask has the form The lack ofcontinuous tone merely generates higher diffracted orders and these areremoved by the mask 61 of FIG. 7. The reference mask containsthefrcquency terms only on one side of zero frequency.

As the signal history on the film 38 moves through the data processor,the image also moves. FIG. 9 illustrates the eti'ect of signal motion onthe zero and two first diffracted order images. The first order imagesmove in opposite directions, as shown in I-IG. 9, while the zero orderimage does not move. If signalfrequencies exist on only one side of thezero frequency, the first order images do not cross the zero orderposition, but fade out instead. The first order image that focuses shortof the zero order image is called the first order positive image, since,with respect to this image, the signal history exhibits a positive focallength. The other first order image focuses beyond the zero order andthis is called the negative first order image, since, with respect tothis image, the signal history exhibits a negative focal length. Eitherthe first order positive image or the first order negative image can beused for focusing on the output slit. Use can be made of the motion ofthe image to increase the exposure of the output film, by widening theoutput slit and choosing the proper camera lens to cause the motion ofthe first order image to correspond to the motion of the film.

Whichever first order image of the signal is used, the other first orderimage :Of the reference function is used. The negative first order imageof the reference function compensates the positive first order image ofthe signal film, and the positive first order image of the referencefunction compensates the negative first order image of the signal film.The slit 60'is located in the proper position to select the requiredreference function image..The reference mask-thusbehaves as a lens withfocal length equal to that of'the signal film focal length, but ofopposite sign. Hence, targetsjfrom all rangcsare imaged at infinity bythe referencefunction signal-film combination. The lens 40 brings thisimage in from infinity to the focal plane of the lens.

Other means for compensating for range requiring less equipment thenshown in FIG. 7 is possible. FIG. 10 shows a system wherein a conicallens 70 is substituted for the reference function. With this system, theprimary slit 51 is locatedoif'of the axis in the position of slit 60 ofFIG. 7. The remainder of the system is the same as FIG. 7.

Another method of compensating for the change of focus with rangeisshownin FIG. II. The recording film and output slit could be slanted tocompensate for the change of focus with range, however, a simpler methodis to slant the mask containing the slit 51 as shown in FIG. 11. Anadditional cylindrical lens 71, and also a longer slit and light source,are needed-when slit 51 is slanted.

Still another system which could be used to-cornpensate for focus wouldbe t0 provide an optical system to vary the wave length of the lightused with range thereby producing 'a constant focus and perfect trackingat all ranges. I

The data processor was developed primarily to solve a specific problemin fineresolution radar. However, during the course of theinvestigation, a number of other applications were conceived. Withthedevice of FIG. 7, the positions of the images on the mask 36 consist ofa one-dimensional Fourier analysis of the spatial frequencies of thesignal film 38. Thus, this portion of the system is amulti-channelspectrum analyzer.

The operation involved with the device of FIG. 7 is given by thefollowing equation:

o, Misfits 21,010 w (1) In the special case described f(x, y) representsthe reference function, g(x, y, t) represents the signal history andh(y, r), the output of the optical processor, rep resents the processedradar data.

Integrals of the form of Equation 1 occur for a number of cases, suchas, high resolution radar, Fourier analysis, antenna patterncomputation, cross-correlation, auto correlation, signal detection,biological correlation, signatureanalysis, analog computation and manyothers.

While the operation of the system has been described with parallel, orcollimated, iightimpingent on certain elements, such as the referencefunction and conical lens, it is obvious that the device does notrequire coliimated light for. its operation, although the description,as well as the design, are facilitated by having collimated light atsuch positions. Likewise, the position of the signal film and referencefunction, or signal film and conical lens, can be interchanged. Numeroussuch variants are possible.

' Other functions, which the device of the invention is capable ofperforming by positioning of the slit in mask 61, are amplitudemodulation detection, spectral analysis and filtering and frequencytranslation. It is obvious that there may be many other operations whichcan be performed with the apparatusof this invention.

The lens unit made up of lenses 40 and 42 produces a one dimensionalFourier transformation between the plane of the film 38 and the plane ofthe mask 36, while preserving the other dimension for plural channel oeration. A number of such lens units can be placed in tandem to producesuccessive transformations with respect to one variable, while alwayspreserving the variable of the other direction, namely, the verticaldirection as the figures are drawn. At the successive planes wherein thesuccessive transformations occur, additional transparencies representingfunctions can be placed. There ,fore, complicated system'transferfunctions can be gencrated. Let the functions at successive planes belabeled f, a, b, c etc., where I is regarded as the. input signal and a,b, c produce an overall system transfer function. Let T(p) be the onedimensional Fourier transform of p. Then, the light distribution atsuccessive planes, after the light is transmitted by the'transparenciesof the plane, is p v tion and is the variable generated by the Fouriertransformatlon.

While certain arrangements of the elements have beenv shown, it is to beunderstood that other arrangements might be used. For example, filters55 and 56 need not be in the position shown, but may 'be locatedwherever there is parallel light in the azimuth direction; however,filter 55 must be located between the light source and the signal film.Lens 42 may be located behind slit 35 adjacent relay lens 41, but itsaxis must be rotated degrees with respect to its position as shown inFIG. 4. 7 Thereis thus provided a device for simultaneously processingwave trains in a great number of channels simultaneously.

We, claim: a l. A device for obtaining the integrated product 0 .twofunctions in a plurality of channels simultaneously, comprising: a firsttransparency having thereon a plurality of spatial'frequency functionswith the functions extending in a first direction and the separatechannels extending in a second direction perpendicular to said firstdirec tion, means for illuminating said first transparency withmonochromatic coherent light which is collimated in said firstdirection, a second transparency having a plurality of functionsextending in said first direction with the separate channels extendingin said second direction, a pair of lenses for imaging said firsttransparency upon said second transparency, a first mask in the focalplane of the first lens of said pair of lenses, said mask having a'slitin the position of at least one of the first diffracted order images ofsaid first transparency, a second mask, output means adjacent said mask,means for integrating the output of said second transparency in saidfirst direction and for focusing said output on said mask, said maskhaving an output slit therein in the position of one of the firstdiffracted order images of said second transparency and means includingsaid last named means for imaging the information in the separatechannels in said second direction on said slit.

2. A device for obtaining the inte rated product of two functions in aplurality of channels simultaneously, comprising: a first transparencyhaving thereon a plurality of spatial frequency, functions with thefunctions extending in a first direction and the separate channelsextending in a second direction perpendicular to said first direction,means for illuminating said first transparency with monochromaticcoherent light which is collimated in said first direction, a secondtransparency having a plurality of functions extending in said firstdirection with the separate channels extending in said second direction,a pair of lenses for imaging said first transparency upon said secondtransparency, a first mask in the focal plane of the first lens of saidpair of lenses, said mask having a slit in the position of the firstpositive diffracted order image of said first transparency, a secondmask, output means adjacent said mask, means for integrating the outputof said second transparency in said first direction and for focusingsaid output on said mask, said mask having an output slit therein in theposition of the first negative diffracted order image of said secondtransparency, and means including 'said last named means for imaging theinformation in the separate channels in said second direction on saidslit.

3. An apparatus for processing a signal film, from an airborne coherentside-looking radar, having thereon Doppler frequency azimuth targetinformation along the length of the film and range information acrossthe film,

comprising: a signal film, means for producing a beam 'the light in theazimuth direction, a second mask having anoutput slit therein, outputmeans adjacent said output 'slit, a'first'leu's for integrating thelight information from said signalfilm inthe' azimuth, direction and forfocusing it on said slit," a'second lens which together with said firsttionwith the range direction being parallel to the line of light, -areference transparency between said light source and said film, saidreference transparency having thereon a signal for all rangesrepresenting the ideal Doppler frequency history for targets at allranges of said radar, means located between said first mask and saidreference transparency for collimating the light in the azimuthdirection, a heat reflecting filter and a monochromatic filter betweensaid light source and said signal film, means for collimating the lightpassing through said heat reflecting filter and said monochromaticfilter, a pair of lenses for imaging said reference transparency on saidsignal film, asecond mask in the focal plane of the first of said pairof lenses, said second mask having a slit in the position of at leastone of the first diffracted order images of said reference transparency,a third mask having an output slit in the position of one of the firstdiffracted order images of said signal film, output means adjacent saidoutput slit, means located between said signal film and said third maskfor integrating the light information from said signal film in theazimuth direction and for focusing it on said slit, and

means for imaging the range information from said sig nal film on saidoutput slit.

5. An apparatus forv processing a signal film from an airborne coherentside-looking radar, having thereon Doppler frequency azimuth targetinformation along the length of the film and range information acrossthe film, comprising: a signal film, a first mask having a narrowelongated slit therein, means for illuminating said mask to therebyproduce a thin line light source, means for moving said film throughsaid light in the azimuth direction with the range direction beingparallel to the line of light, a reference transparency between saidlight source and said film, said reference transparency having thereon asignal for all ranges representing the ideal Doppler frequency historyfor targets at all ranges of said radar, means located between saidfirst mask and said reference transparency for collimating the light inthe azimuth direction, a heat refiectingfilter and a monochromaticfilter between said light source and said signnl film, means forcollimating the light passing through said heat reflecting filter andsaid monochromatic filter, a' pair of lenses for imaging said referencetransparency on said signal film, a second mask in the focal plane ofthe first of said pair of lenses, said second mask having a slit in theposition of at least one of the first diffracted order images of saidreference transparency, a third mask having an output slit therein, arecording film, means for moving said recording film past said outputslit, means located'between said signal film and said recording film forintegrating the light information from-said signal film in'the azimuthdirection and for focusing it on said slit, said slit being in theposition of one ofthe first.diffracted order imsgesof said signal filmand means for imaging the range information, from said signal film onsaid output slit.

6. An spparatus for processing a signal fllmfrom an airbornecoherentside-looking radar, having thereon Doppler frequency azimuthtarget information along the length ofthe film and range informationacross the film,

comprising: evsignal film, a first mask having a'narrow elongated slittherein, means for illuminating said'mssk to thereby produce a thin linelight source, means for moving said through said light in the azimuthdirection with the range-direction being parallel to the line of light,a reference transparency between said light source and said film, saidreference transparency having thereon a signal for all rangesrepresenting the ideal Doppler frequency history for targets at allranges of said radar, means located between said first mask and saidreference transparency for collimating the light in the azimuthdirection, a heat reflecting filter and a monochromatic filter betweensaid light source andsaid signalfilm, a pair of lenses for imaging saidreference transparency on said signal film, a second mask in the focalplane of the first of said pair of lenses, said second mask having aslit in the position of the firstpositive diffracted order image of saidreference transparency, a third mask having an output slit therein, arecording film, means for moving said recording'film past said outputslit, an astigmatic lens system located between said signal film andsaid recording film, said lens system having a first lens therein forinte grating the light information from said signal film in the azimuthdirection and for focusing ,it on said slit, said slit being in theposition of the first negative diffracted order image of said signalfilm, said lens system having a second lens which together with saidfirst lens images the range information of said signal film on saidoutput slit.

7. An apparatus for processing a signal film from an airborne coherentside looking radar, having thereon Doppler frequency azimuth targetinformation along the length of the film and range information acrossthe film, comprising: a signal film, a first mask having a narrowelongated slit therein, means for illuminating said mask to therebyproduce a thin line light source, means for moving saidsfilm throughsaid light in the azimuth direction with the range direction beingparallel to the line of light, 'a reference transparency between saidlight source and said film, said reference transparency having thereon asignal for all ranges representing the ideal Doppler frequency historyfor targets at all ranges of said radar, means located between saidfirst mask and said reference transparency for collimating the light inthe azimuth direction, a heat reflecting filter and a monochromaticfilter between said light source and said signal film, a pair of lensesfor imaging said reference transparency on said signal film, a secondmask in the focal plane of the first of said pair of lenses, said secondmask having a slit in the position of the first negative diffractedorder image of said'reference transparency, a third mask having anoutput slit therein, a recording film, means for moving said recordingfilm past said output slit, an astigmatic lens system located betweensaid signal film and said recording film, said-lens system having afirst lens therein for integrating the light information from saidsignal film in the azimuth direction and for focusing it on said slit,said slit being in the position of the first positive diffracted orderimage of said signal film, said lens system having a second'lens whichtogether with said first lens images the range information of saidsignal film on said output s it.

8-. An apparatus for processing a signal film from an airborne coherentside-looking radar, with the film having thereon Doppler-"frequencyazimuth target information along-the length of'th'c film and rangeinformation across the film, comprising: a signal film, means forproducing a beam ofmonochromstie light, means for moving said filmthrough said light in the azimuth direction, a first maskhaving a slittherein located between said light beam" producing means and said film,said slit being narrowin the azimuth direction and elongated in therange direction, a reference transparency with a signal thereoncorresponding to the ideal Doppler frequency for all ranges, locatedbetween said first mask and said signal film, means located betweensaidfirstmask and said reference transparency for collimating the iight'inthe azimuth direction, a pair of lens for imaging the referencefunctiomupon said signal film, a second mask located in the focal'planeof the first of said pair'of lenses, said second maskhaving a slit inthe position of at least one of the first diffracted order images ofsaid reference transparency, a recording film, a third mask adjacentsaid film, means for moving said recording film past said third mask, afirst lens for integrating the light information from said signal filmin the azimuth direction and for focusing it on said third mask, saidthird mask having a slit therein in the position of one of the firstdiffracted order images of said signal film, a second lens whichtogether with said first lens images the range information from saidsignal film on said output slit.

9. An apparatus for processing a signal film from an airborne coherentside-looking radar, having thereon Doppler frequency azimuth targetinformation along the length of the film and range information acrossthe film, comprising: a signal film, a first mask having a narrowelongated slit therein, means for illuminating said mask to therebyproduce a thin line light source, means for moving said film throughsaid light in the azimuth direction, a heat reflecting filter and amonochromatic filter between said light source and said signal film, aconical lens located between said collimating means and said signal filmto compensate for changes of focus with range on said signal film, meanslocated between said mask and said conical lens for collimating thelight in the azimuth direction, a recording film, a second mask adjacentsaid film, said second mask having an output slit therein, a first lenslocated between said signal film and said re cording film forintegrating the light information from said signal film in the azimuthdirection and for focusing it on said slit, a second lens which togetherwith said first lens images the range information from said signal filmon said output slit.

10. An apparatus for processing a signal film from an airborne coherentside-looking radar, having thereon Doppler frequency azimuth targetinformation along the length of the film and range information acrossthe film, comprising: a signal film, means for producing a beam ofmonochromatic light, means for moving said film through said light inthe azimuth direction, a first mask having a slit thereinlocated betweensaid beam producing means and said film to permit light to pass along apath through said film, said slit being narrow in the azimuth directonand elongated in the range direction, said mask being tilted withrespect to said beam path in the longer dimension of said slit, meanslocated'between said mask and said film for collimating the light in theazimuth direction, a cylindrical lens with its axis perpendicular togreater dimension of said slit located between said collimating meansand said signal film, a recording film, a second mask adjacent saidfilm, said second mask having an output slit therein, an astigmatic lenssystem located 1 between said signal film and said recording film, saidlens system having a first lens therein for integrating the lightinformation from said signal film in the azimuth direction and forfocusing it on said slit, said lens system having a second lens whichtogether with said first lens images the range information from saidsignal film on said output slit.

References Cited UNITED

1. A DEVICE FOR OBTAINING THE INTEGRATED PRODUCT OF TWO FUNCTIONS IN APLURALITY OF CHANNELS SIMULTANEOUSLY, COMPRISING: A FIRST TRANSPARENCYHAVING THEREON A PLURALITY OF SPATIAL FREQUENCY FUNCTION WITH THEFUNCTIONS EXTENDING IN A FIRST DIRECTION AND THE SEPARATE CHANNELSEXTENDING IN A SECOND DIRECTING PERPENDICULAR TO SAID FIRST DIRECTION,MEANS FOR ILLUMINATING SAID FIRST TRANSPARENCY WITH MONOCHROMATICCOHERENT LIGHT WHICH IS COLLIMATED IN SAID FIRST DIRECTION, A SECONDTRANSPARENCY HAVING A PLURALITY OF FUNCTIONS EXTENDING IN SAID FIRSTDIRECTION WITH THE SEPARATE CHANNELS EXTENDING IN SAID SECOND DIRECTION,A PAIR OF LENSES FOR IMAGING SAID FIRST TRANSPARENCY UPON SAID SECONDTRANSPARENCY, A FIRST MASK IN THE FOCAL PLANE